The Anycubic Photon is a great, very inexpensive resin 3D printer. I got it to try and make machine parts and to learn how to design parts for 3D printing.
One issue it has is the Z-axis is not very stable and the very slight side-to-side movements can cause ‘z-wobble’ (this is corrected in the new Photon S model). This z-wobble can mean the prints have may have horizontal banding on the vertical edge.
I had some spare HGR15 linear rail so decided to upgrade the Z-axis in the printer.
This is the original Z-axis in the Photon. There is a a grove behind the lead screw on which 3 bearings run, if you wobble the blue carriage you can feel it move side to side:
The linear rail was cut in half and attached to the sides of the existing aluminium support. Using my Taig mill I cut a new supporting plate and attached to the linear guides with angle pieces. All of this had to be done very accurately on a mill to avoid binding of the rails.